MEMS switches have a wide variety of uses. They can, for example, conduct RF current in applications involving the use of antenna phase shifters, in the tuning of reconfigurable antenna elements and in the fabrication of tunable filters.
MEMS switches provide several advantages over conventional switches which use transistors. These advantages include lower insertion loss, improved electrical isolation over a broad frequency range, and lower power consumption. Also, as this type of switch is fabricated using existing integrated circuit (IC) processing technologies, production costs are relatively low. Thus, MEMS switches manufactured using micromachining techniques have advantages over conventional transistor-based switches because the MEMS switches function like macroscopic mechanical switches, but without the associated bulk and relatively high cost.
The energy that must be moved through the switch control in order to activate the MEMS switch, and thus the energy dissipated by the MEMS switch, is a function of the actuation voltage. Therefore, in order to minimize the energy dissipated by the MEMS switch, it is desirable to minimize the actuation voltage of the switch.
Current MEMS switches operate through adoption of electrostatic techniques. In order to have low actuation voltages (about 50 V), existing electrostatic actuation switches need to have relatively large (about 300 to 500 microns) lateral dimensions. This results in an increased response time. A substantial reduction in the size of these switches is not possible as that significantly increases the actuation voltages. Therefore, electrostatic actuation MEMS switches cannot be further miniaturized as required for further applications. The large dimensions also reduce the restoring force for switch release, thus contributing to a ‘stiction’ problem that essentially renders the switch useless. In particular, the contacting pads tend to adhere to each other after a prolonged use.
Piezoelectric structures can be used to realize tunable capacitors, as disclosed in “Micromachined RF Mems tunable capacitors using piezoelectric actuators”, Jae Y. Park, Young J. Yee, Hyo J. Nam, and Jong U. Bu, IEEE 2001.
In view of the foregoing, there is a need for a micro-electromechanical switch having a low actuation voltage and a fast response time.